The present invention relates to photographic apparatus, and more particularly to improvements in film transporting mechanisms for roll film. Still more particularly, the invention relates to improvements in manually operated film transporting mechanisms which can be utilized with advantage in still cameras to advance the film by the length of a frame between successive exposures of film to scene light.
It is already known to provide a still camera with a film transporting mechanism employing a rapid-transport lever or wheel which must be pivoted or rotated through about 180.degree. in order to advance the film by the length of a frame. It is also known to construct such cameras with a view to insure that the rapid-transport lever or wheel can perform one or more additional functions, for example, the cocking of a shutter, the indexing of a multiple flash lamp holder and/or the cocking or stressing of an impeller for percussion type flash lamps. The lever is coupled to a spring which returns it to a starting position upon completion of film transport. The extent to which the film is to be transported in response to pivoting of the lever or in response to rotation of the wheel is normally determined by a scanning device which engages the film and enters one of a series of perforations when a flash film frame registers with the picture taking lens of the camera. The film can be provided with one perforation for each film frame. It is also known to use a scanning device in the form of a sprocket wheel which is driven by the film and rotates through 360.degree. in response to transport of the foremost unexposed film frame into register with the picture taking lens.
A drawback of such film transporting mechanisms is that the extent of angular displacement of the lever or wheel changes (decreases) from actuation to actuation because the diameter of the roll of exposed film on the takeup reel grows with the number of completed exposures, i.e., the angle through which the takeup reel turns in order to collect successive film frames decreases proportionally with increasing number of exposed film frames to thus necessitate decreasing angular displacements of the rapid-transport lever or wheel. This creates problems when the lever or wheel must perform one or more additional functions because all such functions must be started and terminated during the initial stage of angular movement of the rapid-transport lever or wheel. Consequently, the angular displacement of the lever or wheel from its starting position necessitates the exertion of a substantial force because the lever or wheel must rotate the takeup reel, index a lamp holder, cock the shutter and/or displace a spring-biased impeller practically immediately after it leaves its starting position. Moreover, the camera must be provided with complex couplings, clutches or analogous expensive devices which enable the lever or wheel to move relative to a cocked shutter or impeller or relative to an indexed lamp holder when the lever or wheel must still perform a relatively large angular movement in order to complete the transport of the film by the length of a frame, i.e., before the takeup reel accumulates a relatively large roll of exposed film. Also, the user is likely to break or damage the film transporting and/or other camera mechanism when the transport of film by the length of a frame is completed in response to a relatively small angular displacement of the lever or wheel because the user (especially an inexperienced person) is likely to assume that the transport of film is not completed unless the lever or wheel is always turned through a predetermined maximum angle such as is necessary only when the takeup reel has collected a relatively small number of exposed film frames.